Rheohemapheresis will be performed in 5 cycles. One cycle consists of 2 rheohemapheresis treatments on day 1 and day 4. A cycle lasts for 4 weeks and will be repeated every fourth week. During each treatment > 75% to 100% of patients total plasma volume has to be filtered.General medical reviews, ETDRS and Radner visual acuity assessment, ophthalmologic examinations, ocular imaging with OCT 3, autofluorescein imaging and infrared imaging, multifocal ERG, ocular echography, and blood examinations will be performed.